Let me explain:
Say for example I email the car insurance company or the electricity company with a question and they reply. If I then email again to say "great thanks" is that annoying? Because if everyone who had a question and received an answer responded "ok thanks" then half the emails the person has to wade through are irrelevant really. Does the customer support person sigh when they log on and see 623 new emails. Then as they click through it becomes clear that lots of them are thank yous?
So should I stop responding "ok thanks" or are good manners still important here?
Or if an email comes from a small business what's the story? I emailed a beautician to see if she did X treatment. She replied no. I replied "ok thanks". Am I wasting her time?
(Sorry for wasting everyone's time reading this!)